diff --git a/src/optionstr.c b/src/optionstr.c
index 32663a0..9e9d18f 100644
--- a/src/optionstr.c
+++ b/src/optionstr.c
@@ -259,6 +259,7 @@
     check_string_option(&buf->b_p_cino);
     check_string_option(&buf->b_p_cinsd);
     parse_cino(buf);
+    check_string_option(&buf->b_p_lop);
     check_string_option(&buf->b_p_ft);
     check_string_option(&buf->b_p_cinw);
     check_string_option(&buf->b_p_cpt);
@@ -2102,6 +2103,14 @@
 	parse_cino(curbuf);
     }
 
+    // 'lispoptions'
+    else if (gvarp == &p_lop)
+    {
+	if (**varp != NUL && STRCMP(*varp, "expr:0") != 0
+					       && STRCMP(*varp, "expr:1") != 0)
+	    errmsg = e_invalid_argument;
+    }
+
 #if defined(FEAT_RENDER_OPTIONS)
     // 'renderoptions'
     else if (varp == &p_rop)